Determining the deformation pattern and the development systems of mylonites considering shear sense indexes study and quartz grains dynamic and kinematic investigation.(Qulanji1:50000sheet

Category Tectonic & Seismotectonic
Group GSI.IR
Location 20th symposium on geosciences
Holding Date 16 April 2008

     The study area is situated in Qulanji sheet, northeast of Orumieh. and is part of the Sanandaj-Sirjan tectonic province. Outcrops of the area are basically composed of ultramalic. matic. and acidic rocks that are intruded into a sedimentary sequence. The present study suggests that these rocks are in fact mylonitic rocks that were subjected to syn—tectonic metamorphism. Field studies, study of shear sense indicators, and kinematic study of quartz grains indicate that mylonitic rocks of the study area may be classified into two groups on the basis of their origin: 1 . Mylonites in which the foliation is NW-SE striking, parallel to the Zagros structural trend, and which were developed in ductile compressional strain field. These mylonites show a partial transcurrent (right—lateral) component of shear and were developed at low strain rate (low flow stress) during a thrusting event. 2. Mylonites in which the filiation is NE-SW striking, and were developed in an extensional strain field. The strain is indicated to he of pure shear and plane character. Some component of simple shear and compressional strain is also evident in these mylonitic rocks. The strain in this group of rocks has occurred at high strain rate and high flow stress, and the kinematic indicators show both sinistral and dextral sense for the transcurrent component of shear in these rocks. The latter evidences are in accod with a conjugate shear system model.